In both combat and civilian aircraft, new aircraft designs are moving towards `glass cockpits’, the use of television-type Cockpit Display Units (CDUs) which can be switched to display a wide range of different information, in full colour. This is often known as EFIS electronic flight information systems. In combat aircraft this means that a large number of individual instruments can be replaced by one or two screens. The information which is not needed during that part of the flight is not displayed, but the different display modes will show information which is relevant to the type or phase of mission that is being flown. For instance, a display could show a moving map, so that the aircraft location is kept fixed in the centre of the display and the map moves underneath it. When a weapon is selected, the display can then show all the information required to use that system.
Modern transport aircraft now use multi-mode LCDs (liquid crystal displays) or CRT (cathode-ray tube) displays as the main set of flight instruments, with `real’ instruments used for back-up only. The screens can also show other information, such as engine, navigation and fault data. They can also show maintenance data and previous fault information, and even the maintenance handbooks, for use by the ground maintenance engineers. Each display can be switched to provide the required information, and the source of data can also be switched. So in the event of a fault in the display itself, or in the systems that provide the information and processing to drive the displays, little inconvenience or hazard is presented, and multiple back-up facilities are provided. Glass cockpit systems are extremely flexible, and can be set up to give the information in a way which is most easily read and understood by the crew.
In commercial aircraft too, avionics upgrades to digital avionics with liquid crystal displays reflect these developments.
Head-up displays HUDs
During flight, and in combat, a pilot needs to spend as little time as possible looking down at instrument panels, and concentrate on what is happening outside. But the pilot still needs the information that the aircraft instruments provide. All combat aircraft have a solution now, the head-up display (HUD). The HUD consists of a projection system and a glass reflector. This is located directly in the pilot’s line of sight, but the pilot can see through the glass. At the same time, it reflects an image generated by the HUD projector showing the most important information from the instruments. The information appears as part of the pilot’s view at all times. As well as flight data, the HUD will show information such as gun sights, target marking and weapons data.